The present invention relates to an automatic door lock in general. More particularly, this invention pertains to an automatic door lock provided with a locking shaft which is loaded in the direction of closing the door wing with a spring arrangement, and having a hydraulic piston-cylinder unit with a displacable piston, which effects the rotation of the locking shaft and serves the purpose of dampening the piston's movement.
Door locks of the type under discussion have been designed to hold the door wing normally in the closed position, to enable the closed door to perform such protective functions as protection against fire, sun rays, noise, burglary and maintaining privacy behind the closed door. Such doors are usually provided with a door lock having a hydraulic damping means which has a spring arrangement with the aid of which an energy required for automatic closing of the door is stored during opening of the door by hand and then used, after the door has been completely opened, for closing of the door wing. The automatic movement of the door in the closing direction is damped by means of a hydraulic throttle system and therefore such doors provide for a great comfort, reliability and safety in use.
Available door locks, although they correspond to the present standards should nevertheless provide for a reliable and safe closing of the door wing and also should ensure the safety and quietness by the above noted hydraulic damping system. The door locks with hydraulic damping are standardized; however the quality requirements and the control lines of these locks have been constantly improved.
Although conventional door locks correspond to high technical standards one of the disadvantages of known door locks resides in that an energy required for the closing movement of the door wing must be first applied by a person during the opening movement of the door. This disadvantage makes it particularly difficult or even impossible to handle large and heavy doors, particularly to children or older weak persons. Very often it is impossible to close or open such a door to without help by another person.
To avoid some problems in conventional door locks a door lock has been suggested, provided with a special locking arrangement which has been disclosed, for example in German patent publication DE-OS 25 41 790. In the reference door lock arrangement, the door wing is adjusted to a predetermined opening angle. The return flow opening formed in the piston of the reference arrangement is closed by a needle insertable into that opening. Furthermore, this return flow opening in the piston, closeable by the needle has a return flow passage provided with a throttle arrangement. This return flow passage can be opened or closed through an electromagnetic holding valve. When this return flow passage is closed by the electromagnetic holding valve the door wing remains in the open position only when the return flow conduit located in the piston of the door lock is closed by the needle. First, when the electromagnetic holding valve is opened in the case of danger, the lock spring is in the position in which the piston and the door wing therewith are moved to the closed position. Such doors should be constantly watched because in the case of certain emergencies, such as fire, the special locking arrangement of the door must be released to give to the door wing the necessary property of self closing.
In the other door locks, one of which is for example disclosed in German patent publication DE-OS 2751859, the disadvantage of an uneasy opening of the door wing is overcome in that the energy for the opening process is stored during the closing of the door. In the reference device a so-called free-running door lock is employed, in which the lock spring is blocked in its prestressed position and in which a second piston is interconnected between the first piston, arranged in engagement with the locking shaft, and the lock spring. The return flow conduit extended through the second piston is eventually closed or opened in the case of danger, by means of an electromagnetic control valve. Under normal conditions the pressure medium does not flow out from the pressure space of the first piston arranged in engagement with the locking shaft because the return flow conduit is closed, so that the pistion connected to the locking shaft can be displaced without any resistance in two opposite directions within the pressure space of the cylinder whereby the door wing coupled to the locking shaft can be easily opened or closed by hand. It is obvious that the door remains in its open position if a person does not close it by hand, and therefore the door lock of such a door wing must be always coupled with special control devices, such as smoke alarm systems or fire detecting devices, which, in the case of danger, would close the door wing automatically.
A further disadvantage of conventional door locks is that the door wing should be allowed to remain open of closed for safety purposes although modern people certainly prefer to have automatically closing doors everywhere.
So-called door automates have been suggested, through which the door wing can be automatically opened before a person entering the building or closed behind the person leaving the building. These devices are, however, very costly and are of the same type as those described herein above.